Thanks for bringing this to our attention. There is a note in the Tobi readme about possible BOM substitutions but it appears the schematic shows an invalid configuration. I will change this to reflect our most common setup (TPS62111).


Sorry for the confusion,


On Fri, Aug 30, 2013 at 2:42 PM, the suicidal eggroll <suicidaleggroll@gmail.com> wrote:
I've just finished prototyping a custom Overo expansion board based on the
Tobi, and in the process discovered a problem with the published schematic
for the Tobi dating back many revisions (not sure how far back it's a
problem, but it's far).

The 3.3v regulator used on the Tobi is the TPS62111, a fixed 3.3v output
DC/DC regulator.  According to the data sheet:

FB is the feedback pin that controls the output voltage.  On the adjustable
versions of the regulator (TPS62110, TPS62113) this should be connected to a
voltage divider to set the output voltage, but on the fixed output versions
of the regulator (TPS62111 and TPS62112) it should be connected directly to

The physical Tobi board is constructed correctly, C12 and R34 are not
populated and R33 is a 0 ohm jumper to short FB to Vout.  However, the Tobi
schematic does not reflect this.  The schematic shows a voltage divider
between R33 and R34 which should not be there.

When the circuit shown in the schematic is implemented, the voltage divider
causes the TPS62111 to ramp up Vout since FB is so low.  My 3.3v rail was
hovering around 4.9v until I discovered this problem.  When I removed R34
and C12 and replaced R33 with a jumper, the 3.3v rail dropped down to

Like I said above, the Tobi board itself is fine, but the schematic posted
on pubs.gumstix.com does not match what's actually being built and sold.

View this message in context: http://gumstix.8.x6.nabble.com/Tobi-schematic-error-tp4967841.html
Sent from the Gumstix mailing list archive at Nabble.com.

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